Extremely High-Gain Source Gated Transistors

“Novel thin-film transistors (TFTs) offering significant performance improvements in flexible electronics and displays. Lower power usage and brighter displays open new opportunities, offer manufacturing and cost benefits for industry and higher customer satisfaction for end users”


Background

Although the development of oxide semiconductors for thin-film electronics has brought great opportunities for large-area flexible displays, wearable healthcare devices and virtual-reality, major barriers still prevent large-scale adoption. Indium-gallium-zinc-oxide (IGZO), for example, is nearing maturity, but problems remain in stability (preventing continuous usage) and scalability (limiting the aperture ratios of pixels, inhibiting improvements in picture quality).

The move from rigid silicon-based electronics to flexible electronics further complicates matters. Precise lithography is required to enable large-area device uniformity and registration between different TFT layers. Oxide semiconductor TFTs also lag silicon transistors in their ability to amplify signals, making them uncompetitive for use in sensors.

A research team at The University of Manchester has developed a Source Gated Transistor (SGT) design that overcomes several major obstacles to using oxide semiconductors in large-scale applications and expands the range of available channel materials. These transistors have the potential to be a new fundamental component for thin-film electronics.

The Benefits

  • Increased resolution and brightness with improved picture quality if used in display backplane drivers
  • Lower operating voltage leading to lower power consumption
  • Greater bias stress stability reducing fluctuations in pixel brightness
  • Complete compatibility with industrial design and fabrication techniques
  • Reduced requirement for precise patterning enabling use of less complex fabrication methods, such as printing, and hence reducing manufacturing cost
  • Shorter channel lengths enabling greater pixel density
  • Channel no longer must be a semiconductor, giving increased choice of materials
  • Room temperature deposition, compatible with flexible and transparent substrates
  • High voltage-gain improves the lower limit of detection in sensors
  • Fewer transistors needed in amplifier circuits


The Technology

The invention includes a method for manufacturing TFTs with extremely high voltage-gain using Schottky source contacts and a subsequent pixel design that utilises the properties of these oxide semiconductor TFTs. Intrinsic gains are consistently above 10,000, peaking around 29,000. The same devices demonstrate almost total immunity to negative bias illumination temperature stress, the principal barrier to using oxide semiconductors in major applications, such as display drivers. The devices also display no obvious short-channel effects down to 360 nm, an order of magnitude smaller than typical IGZO TFTs.
[Ref: PNAS March 12, 2019 116 (11) 4843-4848]

Figure 1 (A) Structure and conduction path in a TFT with ohmic contacts.
(B) Structure and conduction path in a TFT with Schottky contacts showing how the current saturates due to depletion under the source.

The new design demonstrates:

Short SGT channel length No short channel effect down to 360 nm
Resistance to Negative Bias Illumination Temperature Stress No discernible effect
Extremely high intrinsic gain 19,000 at VG = 10 V
29,000 at VG = 20 V

Opportunity

UMIP is seeking interest from companies operating in relevant sectors for discussions about collaboration and licensing.

 

UMIP Contact

Please address commercial enquiries about High Gain SGTs, quoting Opportunity No. 20180034, to:

Simon Clarke, IP Development and Partnering Manager
UMIP, Core Technology Facility, 46 Grafton Street, Manchester M13 9NT
E: simon.clarke@umip.com / T: 44 (0) 161 306 8510

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